Manipulating and quantifying temperature-triggered coalescence with microcentrifugation
Feng Huanhuan, Huanhuan ; Ershov, D.S. ; Krebs, T. ; Schroën, C.G.P.H. ; Cohen Stuart, M.A. ; Gucht, J. van der; Sprakel, J.H.B. - \ 2015
Lab on a Chip 15 (2015)1. - ISSN 1473-0197 - p. 188 - 194.
disjoining pressure - droplet formation - emulsions
In this paper we describe a new approach to quantify the stability and coalescence kinetics of thermally switchable emulsions using an imaging-based microcentrifugation method. We first show that combining synchronized high-speed imaging with microfluidic centrifugation allows the direct measurement of the thermodynamic stability of emulsions, as expressed by the critical disjoining pressure. We apply this to a thermoresponsive emulsion, allowing us to measure the critical disjoining pressure as a function of temperature. The same method, combined with quantitative image analysis, also gives access to droplet-scale details of the coalescence process. We illustrate this by measuring temperature-dependent coalescence rates and by analysing the temperature-induced switching between two distinct microscopic mechanisms by which dense emulsions can destabilise to form a homogeneous oil phase.
Effect of surface wettability on microfluidic EDGE emulsification
Maan, A.A. ; Sahin, S. ; Mujawar, L.H. ; Boom, R.M. ; Schroen, C.G.P.H. - \ 2013
Journal of Colloid and Interface Science 403 (2013). - ISSN 0021-9797 - p. 157 - 159.
droplet formation - microchannel emulsification - emulsions - water
The effect of wettability on microfluidic EDGE emulsification was investigated at dispersed phase contact angles between 90 and 160. The highest contact angle (160) produced monodispersed emulsions with droplet size 5.0 lm and coefficient of variation
Preparation of monodispersed oil-in-water emulsions through semi-metal microfluidic EDGE systems
Maan, A.A. ; Boom, R.M. ; Schroën, C.G.P.H. - \ 2013
Microfluidics and Nanofluidics 14 (2013)5. - ISSN 1613-4982 - p. 775 - 784.
t-shaped microchannel - droplet formation - membrane emulsification - polymer microchannels - channel structure - y-junctions - microspheres - devices - model - array
EDGE (Edge-based Droplet GEneration) emulsification systems with the ability to produce multiple droplets simultaneously from a single nozzle, were used for the preparation of monodispersed oil-in-water emulsions. The devices (with plateau height of 1 µm) were coated with metals (Cu, CuNi and CuNi/Cu) and had different surface roughness and wettability properties. This influenced the emulsification behavior significantly. The large surface roughness of the CuNi/Cu coated system resulted in stronger non-uniform filling of the plateau as compared to the smoother surfaces of Cu and less rough CuNi, and less droplet formation points in the CuNi/Cu coated system relative to the Cu and CuNi systems. The less hydrophilic CuNi surface, however, provided wider pressure stability than the more hydrophilic Cu and CuNi/Cu surface. A narrower pressure stability (Cu surface) and lower number of droplet formation points (CuNi/Cu surface) resulted in lower overall droplet formation frequency when compared with CuNi system. All metal coated EDGE systems reliably produced monodispersed droplets (with sizes being 6 times the plateau height), similar to the silicon-based EDGE systems having much smoother surfaces. The pressure stability for CuNi coated surfaces was wider, while the droplet formation frequency was comparable to that with the silicon system. This indicated that the use of metal is not a limitation in these systems as initially expected, but may be used for more robust and productive emulsification systems, which lend themselves well for scale-out to practical productivity rates.
Monodispersed water-in-oil emulsions prepared with semi-metal microfluidic EDGE systems
Maan, A.A. ; Schroën, C.G.P.H. ; Boom, R.M. - \ 2013
Microfluidics and Nanofluidics 14 (2013)1. - ISSN 1613-4982 - p. 187 - 196.
premix membrane emulsification - droplet formation - microchannel emulsification - microcapsules - devices
Monodispersed water-in-oil emulsions were prepared with EDGE (Edge based Droplet GEneration) systems, which generate many droplets simultaneously from one junction. The devices (with plateau height of 1.0 µm) were coated with Cu and CuNi having the same hydrophobicity but different surface roughness. Emulsification was performed by using water as dispersed phase and oils with different viscosities (hexadecane, decane, hexane and sunflower oil) as continuous phases; lecithin, polyglycerol polyricinoleate (PGPR) and span80 were used as emulsifiers. The roughness affected the emulsification behaviour significantly. The smoother Cu surface exhibited droplet formation over the entire length of the droplet formation unit, while the rougher CuNi surface showed non-uniform filling of the plateau and much lower droplet formation frequency. In spite of this different behaviour, monodispersed droplets (CV
High throughput vegetable oil-in-water emulsification with a high porosity micro-engineered membrane
Wagdare, N.A. ; Marcelis, A.T.M. ; Ho, O.B. ; Boom, R.M. ; Rijn, C.J.M. van - \ 2010
Journal of Membrane Science 347 (2010)1-2. - ISSN 0376-7388 - p. 1 - 7.
droplet formation - microchannel emulsification - emulsions - stability - junction - surface - size
Emulsification with high porosity micro-engineered membranes leads to stable emulsions with a low droplet span when, besides a surfactant in the continuous phase, an additional, suitable surfactant is used in the dispersed phase. This surfactant should exhibit relatively fast adsorption dynamics, which is more critical when the surfactant in the continuous phase has slower dynamics. Dispersed-phase fluxes of up to 92.5 x 10(-6) m(3)/m(2)s could be achieved, which is an order of magnitude higher than previously reported for SPG membrane-based cross-flow emulsification.
Premix emulsification: A review
Nazir, A. ; Schroën, C.G.P.H. ; Boom, R.M. - \ 2010
Journal of Membrane Science 362 (2010)1-2. - ISSN 0376-7388 - p. 1 - 11.
shirasu porous-glass - spg membrane emulsification - performance liquid-chromatography - water-in-oil - droplet formation - agarose beads - interfacial-tension - plga nanoparticles - multiple emulsions - flow
Membrane emulsification is known to be a mild technique that renders narrowly dispersed emulsions at energy inputs that are orders of magnitude lower than in traditional emulsification techniques. Cross-flow membrane emulsification is most investigated and is known for the monodispersity of the emulsions produced; however, this can only be obtained at relatively low disperse phase fraction. For emulsions with higher disperse phase fractions, premix membrane emulsification is an interesting alternative that is in our opinion on the verge of breaking through. Principally, in this mild process, a coarse premix is pushed through a porous membrane leading to a fine emulsion having smaller and uniform droplets, at the expense of relatively low energy input. The mean emulsion droplet size can precisely be tuned by adjusting the pore size, transmembrane pressure and the number of cycles. The process can be used for a range of applications, including shear sensitive products such as double emulsions. The present manuscript provides an overview covering the state of the art, including insights in break-up mechanisms and the preparation of various products, and an outlook on further improvement of the process
Effect of viscosities of dispersed and continuous phases in microchannel oil-in-water emulsification
Dijke, K.C. van; Kobayashi, I. ; Schroën, C.G.P.H. ; Uemura, K. ; Nakajima, M. ; Boom, R.M. - \ 2010
Microfluidics and Nanofluidics 9 (2010)1. - ISSN 1613-4982 - p. 77 - 85.
droplet formation - membrane emulsification - silicon plate - model - generation - emulsions - junction - bubbles - device - array
Although many aspects of microchannel emulsification have been covered in literature, one major uncharted area is the effect of viscosity of both phases on droplet size in the stable droplet generation regime. It is expected that for droplet formation to take place, the inflow of the continuous phase should be sufficiently fast compared to the outflow of the liquid that is forming the droplet. The ratio of the viscosities was therefore varied by using a range of continuous and dispersed phases, both experimentally and computationally. At high viscosity ratio (eta (d)/eta (c)), the droplet size is constant; the inflow of the continuous phase is fast compared to the outflow of the dispersed phase. At lower ratios, the droplet diameter increases, until a viscosity ratio is reached at which droplet formation is no longer possible (the minimal ratio). This was confirmed and elucidated through CFD simulations. The limiting value is shown to be a function of the microchannel design, and this should be adapted to the viscosity of the two fluids that need to be emulsified.
Microfluidic Y-Junctions: A Robust Emulsification System with Regard to Junction Design
Steegmans, M.L.J. ; Schroën, C.G.P.H. ; Boom, R.M. - \ 2010
AIChE Journal 56 (2010)7. - ISSN 0001-1541 - p. 1946 - 1949.
t-shaped microchannel - droplet formation - device - chip
EDGE emulsification for food-grade dispersions
Dijke, K.C. van; Schroën, C.G.P.H. ; Padt, A. van der; Boom, R.M. - \ 2010
Journal of Food Engineering 97 (2010)3. - ISSN 0260-8774 - p. 348 - 354.
in-water emulsions - microchannel emulsification - interfacial-tension - droplet formation - membrane - array
In this paper, we use the Edge-based Droplet GEneration (EDGE) emulsification method to produce food-grade emulsions (including double emulsions) and foams. This newly developed mild technology proved to be very stable and robust in the production of all these products. The products are made with food-grade components in an up-scaled micro device, which does not show any changes in time in wettability and fouling. The size of the droplets and bubbles is as needed for food stuffs. Air bubbles generated with EDGE were much larger than emulsion droplets, which could be explained through the viscosity ratio of the phases and changes in interfacial free energy caused by dynamic interfacial tension effects. In the outlook section of this paper, the obtained results are related to the dimensions of the devices, which are in a practically feasible range, also due to the simplicity of the EDGE structure and its operation. Preliminary estimations show that a 300L system can produce 1 m/h 4% (v/v) emulsion
Dynamic Interfacial Tension Measurements with Microfluidic Y-Junctions
Steegmans, M.L.J. ; Warmerdam, A. ; Schroën, C.G.P.H. ; Boom, R.M. - \ 2009
Langmuir 25 (2009)17. - ISSN 0743-7463 - p. 9751 - 9758.
membrane emulsification - surfactant adsorption - droplet formation - marangoni flow - microspheres - emulsions - oxide) - model
Emulsification in microdevices (microfluidic emulsification) involves micrometer-sized droplets and fast interface expansion rates. In addition, droplets are formed in less than milliseconds, and therefore traditional tensiometric techniques cannot be used to quantify the actual interfacial tension. In this paper, monodisperse droplets formed at flat microfluidic Y-junctions were used to quantify the apparent dynamic interfacial tension during (microfluidic) emulsification. Hexadecane droplets were formed in ethanol-water solutions with a range of static interfacial tensions to derive a calibration curve, which was subsequently used to access the dynamic interfacial tension of hexadecane droplets formed in surfactant solutions. For SDS and Synperonic PEF108, various continuous- and disperse-phase (hexadecane) flow rates were studied, and these conditions were linked to interfacial tension effects, which also allowed convective transport of surfactants to be investiagted. On the basis of these findings, various strategies for the formation of emulsion droplets can be followed and are discussed
A Geometric Model for the Dynamics of Microchannel Emulsification
Zwan, E.A. van der; Schroën, C.G.P.H. ; Boom, R.M. - \ 2009
Langmuir 25 (2009)13. - ISSN 0743-7463 - p. 7320 - 7327.
in-water emulsions - droplet formation - array - channel - cfd - microspheres - prediction - diameter - plate
Microchannel emulsification is an interfacial tension driven method to produce monodisperse microdroplets, or microspheres. In this paper we introduce a model for describing the dynamics of microchannel emulsification based on simple time dependent geometric shape analysis. The model is based on mechanistic principles that simultaneously predicts both process and microchannel geometry effects. The model contains no adjustable (fit) parameters and is thus fully predictive for oil in water emulsification. The model is easy to use and does not require extensive computational time and/or memory. The model was validated by comparison with the experimental results published by Sugiura and co-workers and we found excellent agreement. It was found that the droplet size of oil in water emulsions could be fully predicted using only two dimensionless numbers, an adapted capillary number that also comprises effects of terrace width and height, and the ratio of terrace length over terrace height. Based on these findings, a dimensionless design map could be constructed for a wide range of process conditions and microchannel dimensions
Preparation of double emulsions by membrane emulsification - a review
Graaf, S. van der; Schroën, C.G.P.H. ; Boom, R.M. - \ 2005
Journal of Membrane Science 251 (2005)1-2. - ISSN 0376-7388 - p. 7 - 15.
seed oil microdroplets - arterial-injection chemotherapy - dynamic interfacial-tension - water multiple emulsions - hepatocellular-carcinoma - microchannel emulsification - w/o/w emulsion - droplet formation - aqueous vesicles - phase inversion
Double emulsions have potential for the production of low calorie food products, encapsulation of medicines and other high value products. The main issue is the difficulty to efficiently produce double emulsions in a well controlled manner due to their shear sensitivity. In membrane emulsification only mild shear stresses are applied and it is therefore expected that this process is very suitable for the production of double emulsions. In this review an overview is given of the state of the art; the advantages and disadvantages of membrane emulsification in relation to the production of stable double emulsions are summarized and compared. Finally an outlook on further research in this field is given
Status of cross-flow membrane emulsification and outlook for industrial application
Gijsbertsen-Abrahamse, A.J. ; Padt, A. van der; Boom, R.M. - \ 2004
Journal of Membrane Science 230 (2004)1-2. - ISSN 0376-7388 - p. 149 - 159.
shirasu-porous-glass - in-water emulsions - microchannel emulsification - droplet formation - ceramic membranes - microspheres - size - pore
Cross-flow membrane emulsification has great potential to produce monodisperse emulsions and emulsions with shear sensitive components. However, until now, only low disperse phase fluxes were obtained. A low flux maybe a limiting factor for emulsion production on a commercial scale. Therefore, the effects of membrane parameters on the disperse phase flux are estimated. Besides, the effects of these parameters on the droplet size and droplet size distribution are qualitatively described. Wetting properties, pore size and porosity mainly determine the droplet size (distribution). Membrane morphology largely determines the disperse phase flux. As an example, industrial-scale production of culinary cream was chosen to evaluate the required membrane area of different types of membranes: an SPG membrane, an alpha-Al2O3 membrane and a microsieve. Due to the totally different morphologies of these membranes, the fraction of active pores is I for a microsieve and is very low for the other membranes. The choice of the optimal membrane did not depend on the production strategy: either to produce large quantities or to produce monodisperse emulsions, the best suitable was a microsieve with an area requirement of around I m(2). In general, the total membrane resistance should be low to obtain a large disperse phase flux. In contrast, the membrane resistance should be high to obtain monodisperse emulsions when using membranes with a high porosity. (C) 2003 Elsevier B.V. All rights reserved.